GNSS related periodic signals in coordinate time-series from Precise Point Positioning

Abstract

In Global Navigation Satellite System (GNSS) coordinate time-series unrecognized errors and unmodelled (periodic) effects may bias nonlinear motions induced by geophysical signals.Hence, understanding and mitigating these errors is vital to reducing biases and on revealing subtle geophysical signals. To assess the nature of periodic signals in coordinate time-series Precise Point Positioning (PPP) solutions for the period 2008-2015 are generated. The solutions consider Global Positioning System (GPS), GLObalnaya NAvigatsionnaya Sputnikovaya Sistema (GLONASS) or combined GPS+GLONASS (GNSS) observations. We assess the periodic signals of station coordinates computed using the combined International GNSS Service (IGS) and four of its Analysis Centers (ACs) products. Furthermore, we make use of different filtering methods to investigate the sources of the periodic signals. A faint fortnightly signal in our PPP solution based on Jet Propulsion Laboratory (JPL) products and the existence of an 8 d period for those ACs generating combined GPS+GLONASS products are the main features in the GPS-only solutions. The existence of the 8 d period in the GPS-only solution indicates that GPS orbits computed in a combined GNSS solution contain GLONASS-specific signals. The GLONASS-only solution shows highly elevated powers at the third draconitic harmonic (∼120 d period), at the 8 d period and its harmonics (4 d, 2.67 d) besides the wellknown annual, semi-annual and other draconitic harmonics. We show that the GLONASS constellation gaps before December 2011 contribute to the power at some of the frequencies. However, the well-known fortnightly signal in GPS-only solutions is not discernible in the GLONASS-only solution. The combined GNSS solution contains periodic signals from both systems, with most of the powers being reduced when compared to the single-GNSS solutions. A 52 per cent reduction for the horizontal components and a 36 per cent reduction for the vertical component are achieved for the fortnightly signal from the GNSS solution compared to the GPS-only solution. Comparing the results of the employed filtering methods reveals that the source of most of the powers of draconitic and fortnightly signals are satellite-induced with a non-zero contribution of site-specific errors.

Effects of Spatiotemporal Filtering on the Periodic Signals and Noise in the GPS Position Time Series of the Crustal Movement Observation Network of China

“…However, these results cannot exclude the possibility that the draconitic signal is partly due to site-specific effects as suggested by King and Watson [16] because there are still several peaks visible at the frequencies of the draconitic harmonics and the estimation of the power spectrum has uncertainty. Moreover, these results are consistent to the conclusions of Abraha et al [17].…”

Orbital Artifacts in Multi‐GNSS Precise Point Positioning Time Series

“…There is no single peak visible in the periodogram but rather a broad range of peaks close to each other. Abraha et al (2017) already indicated that these might be associated with the changing number of satellites in the constellation on the example of GLONASS. In the analyzed period, the number of available GPS, GLONASS, and Galileo satellites was constant within ±2 satellites day by day (Figure 1).…”

Spatiotemporal Ocean Tidal Loading in InSAR Measurements Determined by Kinematic PPP Solutions of a Regional GPS Network

“…GPS observations from January 01, 2014, to December 31, 2018 are available from the Scripps Orbit and Permanent Array Center (SOPAC). The GPS observations were processed by the standard procedures of Bernese GNSS software version 5.2 (http://www.bernese.unibe.ch/docs/DOCU52.pdf) in kinematic PPP mode into ambiguity-float solutions [27]. The sample interval is 10min, the elevation cut-off angle is 3°.…”